1. Field of the Invention
The invention relates to a cooling plate made of copper or a copper alloy for blast furnaces.
2. Description of Related Art
A cooling plate known from the related art is disclosed in EP 0 951 371 B1. In the cooling plate several bore holes are provided, for accommodating a cooling medium, especially water, which are connected to a cooling medium intake and a cooling medium outlet via connecting pipes that are welded on at the cold side of the plate. The inner cross section of the connecting pipes is usually adapted to the diameter of the bore holes, Fixing the connecting pipes to the cooling plate, as a rule, is done in that, in the cold side of the plate recesses of small depth are produced that are adapted to the outer diameter of the connecting pipes, then the ends of the connecting pipes at the cooling plate are set into these recesses, and subsequently, the connecting pipes are welded to the cooling plate using fillet welds. In this connection, there is no special processing of the ends of the connecting pipes facing the plate. Usually they are mostly beveled on their inner side so as to ensure a better flow of the cooling medium.
If the connecting pipes are made of copper or a copper alloy, the connecting pipes connected to a steel cooling medium intake and cooling medium outlet are provided with a steel collar at a distance from the cooling plate. A steel collar is required in the case of connecting pipes made of copper or a copper alloy in order to produce a gas-tight weld to the blast furnace wall. Because of that, and also in response to the use of steel connecting pipes, one avoids that, when mounting the cooling plates in a blast furnace, copper has to be welded. Welding copper is technically very laborious and costly, and is connected with great risk of faults.
A further problem is, in a known case, that checking the fillet welds, such as by the use of color penetration testing, especially in the case of Cu welding seams, is technically possible, to be sure, but is involved with considerable expenditure.
Since the connecting pipes have to be welded to the cooling plate on the one side, and on the other side a gas-tight connection, especially by welding, has to be produced between the connecting pipes and the blast furnace wall, because of the thermal expansion of the cooling plate, during use, stresses come about at the welding seams between the cooling plate and the connecting pipes.